Genome analysis of a unique strain of Vibrio cholerae O1 carrying the theird replicon

在本研究中，我们发现3株霍乱弧菌O1分离株TSY216、TSY241和TSY421除了携带两条圆形染色体1 （Ch1; 3.0 Mb）和2 （Ch2; 1.0 Mb）外，还携带一个0.9 Mb的复制子（Ch3）。将携带Ch3的TSY216与霍乱弧菌O1的基因组进行了比较。TSY216与其他流行株的1、2染色体非常相似。然而，Ch3不与Ch1和Ch2共享任何保守区。Ch3编码1031个orf和66个基因，编码20个氨基酸的trna。Ch3的起源和功能仍然无法确定。第三个复制子的大规模基因集的获得可能为产生新的霍乱弧菌o型提供机会。

In this study, we found three isolates TSY216, TSY241, and TSY421, of Vibrio cholerae O1 carrying a 0.9 Mb replicon (Ch3) in addition to the two circular chromosomes, 1 (Ch1; 3.0 Mb) and 2 (Ch2; 1.0 Mb). The genome of TSY216 carrying the Ch3 was compared with that of epidemic V. cholerae O1. The chromosomes 1 and 2 were very similar among TSY216 and other epidemic strains. However, the Ch3 did not share any conserved region with Ch1 and Ch2. Ch3 was found to encode 1,031 ORFs and 66 genes encoding tRNAs for 20 amino acids. The origin and function of Ch3 remain unidentifiable. The acquisition of a large-scale gene set of the third replicon may provide an opportunity to result in a new emerging form of V. cholerae O1.